Insulating glass units (IGUs) are used in windows to reduce heat loss from building interiors during cold weather. IGUs are typically formed by a spacer assembly sandwiched between glass lites. A spacer assembly usually comprises a spacer frame extending peripherally about the unit, a sealant material adhered both to the glass lites and the spacer frame, and a desiccant for absorbing atmospheric moisture within the unit. The margins or the glass lites are flush with or extend slightly outwardly from the spacer assembly. The sealant extends continuously about the spacer frame periphery and its opposite sides so that the space within the IGUs is hermetic. The sealant provides a barrier between atmospheric air and the IGU interior, which blocks entry of atmospheric water vapor.
Typically, sealant is manually applied around a majority of the spacer frame periphery, while leaving a small opening formed through the spacer frame uncovered, or free from sealant. The atmospheric air is evacuated and an inert gas is inserted into the space within the IGU. The inert gas is typically inserted via a needle, however the needle is delicate and easily bent. Additionally, if improperly inserted, the needle scratches the glass of the lites. The evacuation of the atmospheric air and insertion of the inert gas is a rate-limiting step of IGU assembly. A rivet or screw, or other fastener is inserted into the opening, and additional sealant is then applied over the uncovered area. Particulate desiccant is typically deposited inside the spacer frame and communicates with air trapped in the IGU interior to remove the entrapped airborne water vapor, and as such, precludes condensation within the unit.